CoinHSL : Prevent CoinHSL from building in parallel (#6715)
CoinHSL : Prevent CoinHSL from building in parallel (#6715)

CoinHSL does not seem to be able to be built in parallel. This commit forces serial compilation.
iulian787/spack,EmreAtes/spack,krafczyk/spack,tmerrick1/spack,tmerrick1/spack,tmerrick1/spack,mfherbst/spack,tmerrick1/spack,matthiasdiener/spack,krafczyk/spack,LLNL/spack,matthiasdiener/spack,EmreAtes/spack,LLNL/spack,krafczyk/spack,iulian787/spack,EmreAtes/spack,LLNL/spack,mfherbst/spack,krafczyk/spack,matthiasdiener/spack,LLNL/spack,EmreAtes/spack,iulian787/spack,matthiasdiener/spack,mfherbst/spack,mfherbst/spack,iulian787/spack,tmerrick1/spack,mfherbst/spack,krafczyk/spack,LLNL/spack,iulian787/spack,matthiasdiener/spack,EmreAtes/spack